In a double-blind study, subjects were exposed to natural sunlight after taking either of two tetracycline antibiotics or placebo capsules for one week. Mild, transient, abnormal sunburn reactions, paresthesias, or both, developed in 11 of 15 subjects who took doxycycline and in none of the subjects who took minocycline or placebo capsules. Tingling and burning of the extremities and other exposed parts was a highly sensitive indicator of abnormal reactions to sunlight.
Frost P, Weinstein GD, Gomez EC. Phototoxic Potential of Minocycline and Doxycycline. Arch Dermatol. 1972;105(5):681-683. doi:10.1001/archderm.1972.01620080011005